78 RESEARCH IN PROTOZOOLOGY 



1928) and demonstrate that when fecal material containing tropho- 

 zoites of T. Jwminis is kept at room temperature (about 

 21 °C. = 70° F.) no conspicuous diminution in the number of 

 flagellates occurs for the first few hours, but after forty-eight or 

 seventy-two hours very few remain alive ; these persist for as long 

 as eight days. Sufficient time is thus allowed for the transfer of 

 viable specimens to the food or drink of man. Feces, containing 

 large numbers of T. Jwminis, were deposited on garden soil in 

 the shade during a wet, cloudy period when the temperature 

 ranged from I2°C. (54°F.) to I9°C. (66°F.). Only a slight 

 decrease in numbers of flagellates was noted during the first twen- 

 ty-four hours, but very few were present at the end of Seventy- 

 two hours. Cultures of serum-saline-citrate medium inoculated 

 with samples from the fecal mass were positive on the fourth, 

 fifth and seventh days. A similar stool, when deposited on sandy 

 soil, sank below the surface almost immediately. Positive cultures 

 were obtained with contaminated sand at the end of twelve hours, 

 but not later. The character of the soil is thus of considerable im- 

 portance in the viability of T. hominis in localities where soil pol- 

 lution is prevalent. 



When a sample of fecal material containing T. hominis is stirred 

 up in a drop of tap water the flagellates become spherical almost 

 immediately, lose their power of locomotion and change from a 

 bluish green to a transparent appearance. No changes are visible 

 when similar material is stirred up in saline-citrate solution. These 

 effects are attributed principally to changes in the osmotic pressure 

 of the medium. The osmotic pressures of the various materials 

 used as determined by the freezing-point depression method, were 

 as follows: undiluted feces, 6.145, serum-saline-citrate medium, 

 7.710, saline-citrate solution, 7.469, ten grams of feces in ninety 

 cubic centimeters of tap water, 0.603, ^^e grams in ninety-five 

 cubic centimeters, 0.482, and one gram in ninety-nine cubic centi- 

 meters, 0.T2I. It, therefore, seems evident that there is plenty of 

 opportunity for trichomonads to reach new hosts in a viable condi- 

 tion but that there is very little danger of infection due to contami- 

 nated drinking water since the flagellates are killed very quickly 

 in this medium. 



Experiments by the writer (Hegner, 1928) and others indicate 

 that flies may serve as important transmitting agents oi T. hominis 

 but that cockroaches probably do not, since most of the trichom- 



